<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <p>
            计数器：{{counter}}
        </p>
        <button @click="add">+</button>
        <button @click="sub">-</button>

    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    <script>
        var app = new Vue({
            el:'#app',
            data:{
               counter: 0,
            },
            methods:{
                add(){
                    this.counter ++;  //这里的this就是app这个对象
                },
                sub(){
                   this.counter--;
                }

            }
        })
    </script>
</body>
</html>